The visir_spc_reduce recipe

visir_spc_reduce

Synopsis

Spectroscopic Observation recipe

Description

This recipe performs a wavelength calibration followed by spectrum extraction from a combined image. It can also compute sensitivities for standard star observations.

It works for low and high resolution including echelle mode.

The files listed in the Set Of Frames (sof-file) must be tagged: VISIR-Long-Slit-Spectroscopy-file.fits SPEC_OBS_LMR VISIR-Quantum-Efficiency-Calibration-file.fits SPEC_CAL_QEFF VISIR-Atmospheric-Emission-Lines-Calibration-file.fits SPEC_CAL_LINES VISIR-Standard-Star-Flux-Catalog.fits (optional)SPEC_STD_CATALOG VISIR-linearty-table.fits LINEARITY_TABLE (optional) Additionally, a bad pixel map with a PRO.CATG of IMG_BPM may be added to the Set Of Frames with tag: BPM.

Constructor

cpl.Recipe("visir_spc_reduce")

Create an object for the recipe visir_spc_reduce.

import cpl
visir_spc_reduce = cpl.Recipe("visir_spc_reduce")

Parameters

visir_spc_reduce.param.planestart

Plane number to start repacking from in each nod cycle,earlier planes are skipped. (int; default: 0) [default=0].

visir_spc_reduce.param.planelimit

Limit number of processed inputplanes. It will repack until at least this number of input images have been processed or the full dataset has been repacked. Always full chop cycles need to be repacked so the number is adjusted upward to the next multiple of images per chop cycle. <= 0 for no limit. (int; default: -1) [default=-1].

visir_spc_reduce.param.trimlow

Burst data only. Number of additional planes to cut from before each plane with chopper movement. (int; default: 0) [default=0].

visir_spc_reduce.param.trimhigh

Burst data only. Number of additional planes to cut from after each plane with chopper movement. A value of -1 does not skip the plane of the movement. (int; default: 0) [default=0].

visir_spc_reduce.param.lincorrect

Apply linearity correction. Should only be enabled on high flux observations, may degrade results otherwise. (bool; default: False) [default=False].

visir_spc_reduce.param.xl

Coordinate in spatial direction. Together with yl it defines the lower point of a rectangle containing only skylines for the wavelength shift detection (int; default: 117) [default=117].

visir_spc_reduce.param.yl

Coordinate in wavelength direction. See xl (int; default: 110) [default=110].

visir_spc_reduce.param.xh

Coordinate in spatial direction. Together with yl it defines the higher point of a rectangle containing only skylines for the wavelength shift detection (int; default: 125) [default=125].

visir_spc_reduce.param.yh

Coordinate in wavelength direction. See xh (int; default: 150) [default=150].

visir_spc_reduce.param.slit_skew

Distortion correction: Skew of slit (degrees) (clockwise) (float; default: 0.52) [default=0.52].

visir_spc_reduce.param.spectrum_skew

Distortion correction: LMR Skew of spectrum (degrees) (counter- clockwise). Not used in High Resolution (float; default: 1.73) [default=1.73].

visir_spc_reduce.param.vert_arc

Distortion correction: LR Detector vertical curvature (pixel). Reduced by a factor 4 in MR. Not used in HR A-side. Increased by a factor 115/52 in HR B-side (float; default: -0.8) [default=-0.8].

visir_spc_reduce.param.hori_arc

Distortion correction: LMR Detector horizontal curvature (pixel). Increased by a factor 1.5 in HR A-side. Reduced by a factor 2 in HR B-side (float; default: 0.0) [default=0.0].

visir_spc_reduce.param.destripe_iterations

Max number of destriping iterations (0 to disable destriping). Horizontal destriping is done first and if no horizontal striping is detected, vertical destriping is performed (int; default: 15) [default=15].

visir_spc_reduce.param.destripe_morpho

Destripe with morphological cleaning (bool; default: False) [default=False].

visir_spc_reduce.param.rej

Each resulting pixel is the average of the corresponding (interpolated) pixel value in each jittered image. A positive value, n1, for the first of the two integers specifies that for each pixel the smallest n1 pixel values shall be ignored in the averaging. Similarly, a positive value, n2, for the second of the two integers specifies that for each pixel the largest n2 pixel values shall be ignored in the averaging. (str; default: ‘0-0’) [default=”0-0”].

visir_spc_reduce.param.bkgcorrect

Subtract the median from the spectral column before extracting the wavelength. This is required when the skylines do not correctly cancel due to gratting oscillations (bool; default: True) [default=True].

visir_spc_reduce.param.plot

The recipe can produce a number of predefined plots. Zero means that none of the plots are produced, while increasing values (e.g. 1 or 2) increases the number of plots produced. If the plotting fails a warning is produced, and the recipe continues. The default behaviour of the plotting is to use gnuplot (with option -persist). The recipe currently produces 1D-plots using gnuplot commands. The recipe user can control the actual plotting-command used by the recipe to create the plot by setting the environment variable CPL_PLOTTER. Currently, if CPL_PLOTTER is set it must contain the string ‘gnuplot’. Setting it to ‘cat > my_gnuplot_$$.txt’ causes a number of ASCII-files to be created, which each produce a plot when given as standard input to gnuplot (e.g. later or on a different computer). A finer control of the plotting options can be obtained by writing an executable script, e.g. my_gnuplot.pl, that executes gnuplot after setting the desired gnuplot options (e.g. set terminal pslatex color) and then setting CPL_PLOTTER to my_gnuplot.pl. The predefined plots include plotting of images. Images can be plotted not only with gnuplot, but also using the pnm format. This is controlled with the environment variable CPL_IMAGER. If CPL_IMAGER is set to a string that does not contain the word gnuplot, the recipe will generate the plot in pnm format. E.g. setting CPL_IMAGER to ‘display - &’ will produce a gray-scale image using the image viewer display. (int; default: 0) [default=0].

visir_spc_reduce.param.slit_skew

Distortion correction: Skew of slit (degrees) (clockwise) (float; default: 0.52) [default=0.52].

visir_spc_reduce.param.spectrum_skew

Distortion correction: LMR Skew of spectrum (degrees) (counter- clockwise). Not used in High Resolution (float; default: 1.73) [default=1.73].

visir_spc_reduce.param.vert_arc

Distortion correction: LR Detector vertical curvature (pixel). Reduced by a factor 4 in MR. Not used in HR A-side. Increased by a factor 115/52 in HR B-side (float; default: -0.8) [default=-0.8].

visir_spc_reduce.param.hori_arc

Distortion correction: LMR Detector horizontal curvature (pixel). Increased by a factor 1.5 in HR A-side. Reduced by a factor 2 in HR B-side (float; default: 0.0) [default=0.0].

visir_spc_reduce.param.fixcombi

Perform the distortion correction on the combined image, and not on each of the jittered images. This will reduce excution time and degrade the quality of the combined image (bool; default: False) [default=False].

visir_spc_reduce.param.emis_tol

The computation of the mean and standard deviation of the sensitivity is done for wavelengths with an atmospheric emissivity of at most emis_min + emis_tol * (emis_max - emis_min), where emis_min is the minimum emissivity in the observed wavelength range and emis_max is the ditto maximum. Thus emis_tol = 1 means that all wavelengths are included. (float; default: 1.0) [default=1.0].

visir_spc_reduce.param.destripe_iterations

Max number of destriping iterations (0 to disable destriping). Horizontal destriping is done first and if no horizontal striping is detected, vertical destriping is performed (int; default: 15) [default=15].

visir_spc_reduce.param.destripe_morpho

Destripe with morphological cleaning (bool; default: False) [default=False].

visir_spc_reduce.param.rl

Reject leftmost columns in spectrum extraction, zero means all columns on the left are used. In cross-dispersion mode a (small) negative number may be used (pixel) (int; default: 0) [default=0].

visir_spc_reduce.param.rr

Reject rightmost columns in spectrum extraction, zero means all columns on the right are used. In cross-dispersion mode a (small) negative number may be used (pixel) (int; default: 0) [default=0].

visir_spc_reduce.param.apfile

An optional ASCII file specification of the aperture definitions to use during spectral extraction. Each line must contain either 3 fields for optimal extraction, or an even number of fields greater than 5 for aperture extraction. For optimal extraction, the 1st field should be ‘O’, and for aperture extraction it should be ‘A’. In both cases the next pair of fields indicate the left & right edges of the source aperture in pixel coordinates. For aperture extraction, fields after the 3rd define the sky apertures coordinates, with the 4th field indicating the method used to determine the sky background [one of ‘A’ (average), ‘F’ (linear fit), or ‘M’ (median)] followed by at least one pair of pixel coordinates representing the left & right edge of a sky aperture. You may supply more sky apertures by supplying additional pixel coordinate pairs after the first. Multiple lines targeting the same order are allowed. (str; default: ‘NONE’) [default=”NONE”].

visir_spc_reduce.param.ro_noise

Readout noise of the detector (float; default: 14.5) [default=14.5].

visir_spc_reduce.param.ox_sigma

Sigma to use for clipping in optimal extraction (float; default: 5.0) [default=5.0].

visir_spc_reduce.param.ox_niters

Number of optimal extraction iterations to perform (int; default: 2) [default=2].

visir_spc_reduce.param.ox_smooth

Width of smoothing window to use along spectral dimension during optimal extraction. A median filter is used. (int; default: 31) [default=31].

visir_spc_reduce.param.gain

Detector gain (float; default: 0.75) [default=0.75].

visir_spc_reduce.param.ox_kernel

Size of square smoothing kernel, in pixels, to apply to science frame before optimal extraction (ignored during aperture extraction). A median filter is used. (int; default: 3) [default=3].

visir_spc_reduce.param.respcal

An optional path to a FITS file containing a 1-D fringe model to be divided into the 1-D extracted spectra in order to remove the fringes. (str; default: ‘NONE’) [default=”NONE”].

visir_spc_reduce.param.delete_temp

Delete temporary files created during processing (bool; default: True) [default=True].

visir_spc_reduce.param.destripe

Attempt to remove stripes (bool; default: False) [default=False].

The following code snippet shows the default settings for the available parameters.

import cpl
visir_spc_reduce = cpl.Recipe("visir_spc_reduce")

visir_spc_reduce.param.planestart = 0
visir_spc_reduce.param.planelimit = -1
visir_spc_reduce.param.trimlow = 0
visir_spc_reduce.param.trimhigh = 0
visir_spc_reduce.param.lincorrect = False
visir_spc_reduce.param.xl = 117
visir_spc_reduce.param.yl = 110
visir_spc_reduce.param.xh = 125
visir_spc_reduce.param.yh = 150
visir_spc_reduce.param.slit_skew = 0.52
visir_spc_reduce.param.spectrum_skew = 1.73
visir_spc_reduce.param.vert_arc = -0.8
visir_spc_reduce.param.hori_arc = 0.0
visir_spc_reduce.param.destripe_iterations = 15
visir_spc_reduce.param.destripe_morpho = False
visir_spc_reduce.param.rej = "0-0"
visir_spc_reduce.param.bkgcorrect = True
visir_spc_reduce.param.plot = 0
visir_spc_reduce.param.slit_skew = 0.52
visir_spc_reduce.param.spectrum_skew = 1.73
visir_spc_reduce.param.vert_arc = -0.8
visir_spc_reduce.param.hori_arc = 0.0
visir_spc_reduce.param.fixcombi = False
visir_spc_reduce.param.emis_tol = 1.0
visir_spc_reduce.param.destripe_iterations = 15
visir_spc_reduce.param.destripe_morpho = False
visir_spc_reduce.param.rl = 0
visir_spc_reduce.param.rr = 0
visir_spc_reduce.param.apfile = "NONE"
visir_spc_reduce.param.ro_noise = 14.5
visir_spc_reduce.param.ox_sigma = 5.0
visir_spc_reduce.param.ox_niters = 2
visir_spc_reduce.param.ox_smooth = 31
visir_spc_reduce.param.gain = 0.75
visir_spc_reduce.param.ox_kernel = 3
visir_spc_reduce.param.respcal = "NONE"
visir_spc_reduce.param.delete_temp = True
visir_spc_reduce.param.destripe = False

You may also set or overwrite some or all parameters by the recipe parameter param, as shown in the following example:

import cpl
visir_spc_reduce = cpl.Recipe("visir_spc_reduce")
[...]
res = visir_spc_reduce( ..., param = {"planestart":0, "planelimit":-1})

See also

cpl.Recipe for more information about the recipe object.

Bug reports

Please report any problems to Julian Taylor. Alternatively, you may send a report to the ESO User Support Department.